Mobile vehicles or robots are used in a variety of applications such as space exploration, material transportation, and civilian, military, and law enforcement. By way of example, mobile vehicles are used by space scientists for planetary exploration, by law enforcement forces for EOD (Explosive Ordnance Disposal), SWAT (Special Weapons and Tactics), and IED (Improvised Explosive Device). Such applications have been in effect since early 90s.
The capability of a mobile vehicle or robot to travel over a wide range of unknown terrains with minimal human interference, even autonomously, is a challenge for designers of mobile vehicles or robots. Notwithstanding, the majority of current mobile vehicle platforms are either wheeled or track-based, or both by manual conversion from one mode to the other. Wheels are suitable for motion over smooth, plain terrain at high speed, whereas tracks are suitable for motion over unstructured terrain, such as stairs, slopes, obstacles, and ditches at lower speed. The major problem in most practical circumstances is that it may be beneficial to switch intermittently between wheels and tracks without manual conversion. If the terrain is unknown or unstructured, or there is a security mission in an urban setting that involves flat terrain (street) and stairs, a wheeled robot may be unsuitable for some of the tasks and a tracked robot may be too slow for most of the tasks.
Some mobile vehicles provide manually reconfigurable track-wheeled locomotion thus offering the advantages of both types of systems; however there are limitations. Manually reconfigurable track-wheeled mobile vehicles can only use one option of mobility at a time. Examples of these are found in US patent application #2009/0266628A1 to Schempf et al., published on Oct. 29, 2009. The inherent limitation in the use of manually reconfigurable track-wheeled mobile vehicles is that the terrain must be known a priori for the operator to select one mode or the other for the required mission that is controlled remotely.
In the case of tracked robots it is known that adding a pair of tracked flippers pivotally attached to both sides of the chassis at one or both ends or at the center of the chassis' side panels enhances the ability of the mobile vehicle to maneuver stairs and overcome obstacles, as shown in U.S. Pat. No. 6,263,989 issued to Won on Jul. 24, 2001 and U.S. Pat. No. 7,493,976 issued to Goldenberg et al. on Feb. 24, 2009. These robots provide remote controlled variable configuration articulated tracked mobile vehicles to ease the overcoming of obstacles.
Another approach is with concurrent operation of tracks and wheels. However, there are disadvantages with this approach due to wheel interference while overcoming obstacles in the track mode and additional loading due to tracks in the wheel mode. Examples of this approach are shown in U.S. Pat. No. 5,022,812 issued to Coughlan et al. on Jun. 11, 1991 and in US patent application #2008/0258550 to Webster et al. and published on Oct. 23, 2008.
Another approach is to run the robot on tracks, and then attach wheels on the pulleys' shafts converting the robot to wheeled, and vice-versa. However, this can only be done manually, not remotely from a distance, or autonomously. Another approach is to run the robot on tracks mounted over the wheels. In this example, when the wheels are to be used, the tracks are manually removed and alternatively, if the robot is running on wheels, tracks can be applied manually over the wheels and locked in place, rendering the mobile vehicle as running on tracks. All these approaches have limitations because of the need to perform the conversions track-wheel and vice-versa manually. Accordingly it would be advantageous to provide a mobile vehicle that can by remote control or autonomously convert between track and wheel modes.